What Reason is the Last One?

"Obligation…" Samuel shook his head and laughed faintly. "Whether you want to help or not is up to you. I can't force you to do what you don't want to do. Even if you have the ability, it's your right to decide what to do with your ability."

He looked into the distance and then said, "Say, how many people do you think will devote their entire ability for the nation and worked for them? For example, many researchers only cares for money and choose to work in private institute because the welfare is better for them and they could earn a lot of money. 

Those who are purer in their research might be wiling to devote to the nation and gave their research result to the nation but can still earn some remuneration that's definitely not comparable to private institute. But how many people are so pure like that?"

Many people are selfish.

They cared for their own benefit more than the entire world.